#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 100010, M= 200010, INF = 0x3f3f3f3f;

int n, m;
int p[N];

struct Edge
{
    int a, b, w;
    bool operator<(const Edge &W) const
    {
        return w < W.w;
    }
}edges[M];

int find(int x)
{
    if(p[x] != x) p[x]= find(p[x]);
    return p[x];
}

int kruskal(){
    sort(edges, edges + m);
    for(int i = 1; i <= n; i ++) p[i] = i;
    int res = 0, cnt = 0;
    for(int i = 0; i < m; i ++)
    {
        int a = edges[i].a, b= edges[i].b, w=edges[i].w;
        a = find(a), b= find(b);
        if(a != b)
        {
            p[a] = b;
            res += w;
            cnt ++;
        }
    }
    if(cnt < n-1) return INF;
    return res;


}

int main(){
    scanf("%d%d", &n, &m);
    for(int i = 0; i < m; i ++)
    {
        int a, b, w;
        scanf("%d%d%d", &a, &b, &w);
        edges[i] = {a, b, w};

    }
    int t = kruskal();
    if(t == INF) puts("impossible");
    else cout << t;

    return 0;
}